CPanel pointing to Custom Squirrelmail

Would anyone know how to get cPanel to point to a different install of squirrelmail in it's own account instead of the one in /usr/local/cpanel/base/3rdparty/, so that when accessing domain.tld/webmail (or domain.tld:2095 or domain.tld:2096) the custom install shows up?

What I've got is an install of squirrelmail in a separate account: mysqm. When I access mysqm.tld it works fine.
If I add an alias in httpd.conf like this:
Alias /sqmail /home/mysqm/public_html/
I get an error when accessing otherdomain.tld/sqmail

Warning: Unknown(): open_basedir restriction in effect. File(/home/mysqm/public_html/index.php) is not within the allowed path(s)

And I don't really won't to enable open__basedir on my accounts... Maybe I've set the rights on the squirrel files wrong (root.wheel)?

And what I'm trying to achieve is to get it to work on port 2096, if I type https://domain.tld:2096 after logging in and choosing squirrelmail I won't to access my install in /home/mysqm/
I'm not sure that this is possible...